engine - remove gncmod boilerplate

engine is now an ordinary shared library

This requires a few more places to run gnc_engine_init as
this is no longer done as part of module loading.

libgnucash/gnc-module/example/gncmod-example.c

@@ -65,10 +65,6 @@ libgncmod_example_gnc_module_description (void)
 int
 libgncmod_example_gnc_module_init (int refcount)
 {
-    if (!gnc_module_load ("gnucash/engine", 0)) {
-        return FALSE;
-    }
-
     if (refcount == 0) {
         /* this is the first time the module is loaded */